The original Trainer (Japanese: おやowner), or OT, of a Pokémon is the Trainer who caught or hatched the Pokémon in question first. The original Trainer's name is used in conjunction with their ID number to verify which Pokémon are outsider Pokémon by the games.

In the games

Pokémon receive the OT of the Trainer who originally caught, hatched, received, or snagged the Pokémon. NPC Trainers who give away Pokémon for free will not be registered as the Pokémon's OT, except for in two instances - a Spearow given by Webster and a Shuckle given by Kirk, both in the Generation II games and their remakes. These special instances are different in that the Pokémon received is intended to be later returned, in Webster's case to his friend on Route 31, and in Kirk's case, to him after Silver has been defeated at Mt. Moon.

A Pokémon bred by a player which is traded as an Egg to another will be registered to the hatching Trainer, while the breeder will not matter. A Shadow Pokémon that has been snagged will initially display its OT as question marks, however, after becoming purified, it will have the person who purified it as its OT, with no mention made of the Trainer it was snagged from.

Effects

While a traded Pokémon doesn't really change in any way (with the obvious exception of those who evolve through this method), a Trainer lacking the proper Badges will be unable to control a Pokémon over a specified level; this issue is only encountered because said Trainer is not the original one. Only the OT can change the nickname of a Pokémon as well. A Pokémon will have a specified ID number (identical to their Original Trainer's) and without any sort of cheating device, it will stay the same as long as the creature's data remains in the game. Traded Pokémon will gain an additional 50% bonus to experience from battles, making them easier to level up. This also applies to experience gotten through Exp. Share—so if a single Pokémon would gain 1000 experience points from a battle, in the case of the Exp. Share division, the Pokémon without the Exp. Share would gain 500 experience points, and the Pokémon with it would gain 750.

N's Pokémon

In Black 2 and White 2, the player will have the opportunity to catch Pokémon that were once used by N via the Memory Link. Though the player is the one that catches these Pokémon, the Pokémon will have N as the OT, making N's Pokémonoutsider Pokémon. Like other outsider Pokémon, N's Pokémon receive boosted experience points.

Trivia

There is a limit to the length of a Trainer's name. Before Generation VI, the limit was five characters in Japanese and Korean versions and seven characters in others. In Japanese versions of Generation III games, there was a bug where the extra two characters of an international Pokémon's OT would not display. This also occurred with the extra five characters in Pokémon names. In Generation VI, the limit is six characters for Japanese and Korean and twelve characters for other languages.